Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$40.42	9.629%	$44.312	$44.31	$44.30	$44.30
Purchase #2	$180.85	8.698%	$196.5803	$196.58	$196.60	$196.60
Purchase #3	$200.95	8.737%	$218.507	$218.51	$218.50	$218.50
Purchase #4	$20.33	7.752%	$21.906	$21.91	$21.90	$21.90
Purchase #5	$220.96	8.142%	$238.9506	$238.95	$238.95	$239.00
Purchase #6	$173.92	7.421%	$186.8266	$186.83	$186.85	$186.80
Purchase #7	$206.70	8.798%	$224.8855	$224.89	$224.90	$224.90
7 purchase totals =	$1,044.13		$1,131.9680	$1,131.98	$1,132.00	$1,132.00